In this work, the vector equation of a straight line, a topic in vector geometry that students often struggle to understand, was investigated in an interactive, immersive augmented reality (AR) experience. In a user test, 28 undergraduate engineering students solved different collaborative tasks using the AR tool during a student-centred learning activity in a university mathematics course. Augmented reality combines virtual content with the reality to a create a coherent experience. Compared to desktop or mobile applications, immersive AR experiences, often using head-mounted displays (HMD), can be more engaging due to its multi-sensory user interaction, such as hand gesturing, spatial movement, and the perception of true three-dimensionality in a stereoscopic view. Due to recent improvements in hardware and decreasing costs, AR has been used more frequently in educational settings. Still, compared to the mobile form factor, HMD-based AR studies are underrepresented. While multiple studies report benefits of AR in education, such as increased student performance, achieving these benefits depends on the context of use and the specific AR implementation. The results of this work suggest that the three-dimensional and dynamic nature of immersive AR is well suited to investigating mathematical concepts such as the vector equation of a straight line. Compared to virtual reality (VR) experiences, immersive AR facilitates peer-to-peer interaction. Students were motivated to use the technology and reported task-related learning outcomes from the activity. For university curricula to benefit from immersive AR, interdisciplinary teams need to share knowledge to create appropriate AR experiences. Moreover, an AR implementation should follow a long-term approach and include students from both educational and technical domains into the design process.